(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 1.2 g pebble is lodged in the tread of a 0.76-m automobile tire, held in place by static friction that can be at most 3.6 N. The car starts from rest and gradually accelerates on a straight road. How fast is the car moving when the pebble flies out of the tire tread?

2. Relevant equations

I looked at the Chapter references and found v=ωR or v=2∏R/T where T=the period of the circle.

3.Attempts

1.I thought of Torque of the wheel but I can't find the Inertia (mass of tire not given) and I have no idea what the magnitude of the force rolling the tire.

2.I tried a=F/m and got a=3.6N/.0012kg=3000 m/s^{2}.

3.I thought of the torque as a result of the static friction and computed τ=3.6N*0.38m=1.368N*m but how do I apply that to find the velocity of the car? I can't use τ=Iα because while I have the mass of the pebble I don't have the mass of the tire and if I used the pebble I don't know the radius of the pebble (if there is one). So this method won't work.

4.V=2∏R/T is useless because the problem does not give me time at all. And I would need time to find the period and/or velocity.

My largest obstacle so far in this course is my trouble in decomposing the components. Would anyone mind helping me get started in solving this problem?

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Velocity required to increase friction?

**Physics Forums | Science Articles, Homework Help, Discussion**